In machining operations which require high speed and accurate thread tapping, the old, floating-type tapper which forcefully pushes a rotating tap into work material has been replaced by an automated rigid-type tapper in which a carriage is rigidly mounted to a base by a lead screw and is turned in synchronization with rotation of the spindle motor. Synchronization is achieved by sophisticated and accurate positional motors which receive commands from a central controller. Either the position of the feed motor which turns the feed screw or the position of the spindle motor is used as a reference to lead the other in a synchronized ratio which corresponds to the pitch of the tap. Rigid-type synchronized tappers, however, have problems maintaining the accuracy of the required spindle rotation and feed advance ratio at high speed. This problem is caused, among other things, by the difference in gearing and inertia between the separate spindle and feed components.